DAMASCUS, SYRIA
— When US troops stormed the rebel-held city of Fallujah last month, they uncovered photos of senior Syrian officials that have further strained the already tense relations between Syria and Iraq, according to the Iraqi ambassador to Syria.

Several captured insurgents were found in possession of the photographs, confirmation, according to Iraqi officials, that some elements in the Syrian regime - perhaps acting independently - are involved in Iraq's bloody insurgency.

"Prime Minister Iyad Allawi wrote a letter to the Syrians saying he had the pictures but was not going to release them despite being under pressure from the Americans to do so," says Hassan Allawi, Iraq's newly appointed ambassador to Damascus.

The ambassador said that the photographs were found in the possession of Moayed Ahmed Yasseen, also known as Abu Ahmed. He is the leader of the Jaish Mohammed group, which is composed of former Baathist intelligence personnel. One picture showed Mr. Yasseen standing beside a senior Syrian official, the ambassador said. He would not identify on the record the Syrian officials in the photos.

US Marines in Fallujah released a report on Nov. 20 that revealed they had discovered a hand-held Global Positioning System receiver with waypoints originating in western Syria and the names of four Syrian foreign fighters contained in a ledger.

The evidence has triggered renewed charges from US and Iraqi officials that Syria is knowingly providing assistance to several former Iraqi Baathists who are believed to be running the insurgency from Damascus.

US Deputy Secretary of State Richard Armitage warned Syria Wednesday that Washington was prepared to impose new sanctions if it failed to clamp down on fugitive Iraqi officials.

Last week, Gen. George W. Casey, the commander of US forces in Iraq, said that the exiled Baathists had formed a group called the New Regional Command and were running the insurgency from Syria.

The Syrians, he said, "are not going after the big fish [or senior Baathists], ... the people that we're interested in."

Ambassador Allawi says that the "real danger" to the Syrian government is not pressure from the US and Iraq, but from the reformed Iraqi Baathist network in Syria.

"There is an Iraqi Baathist invasion of Syria. It's overwhelming," he says. "They stole gold and robbed banks and came here. They have enough funds to keep fighting for 30 years."

Nonetheless, it remains unclear to what extent some of the Iraqi Baathists are involved in the insurgency and what level of assistance is being provided by elements in the Syrian regime. "There is a high level of suspicion but not much evidence," a European diplomat in Damascus says.

The Syrian government rejects the US and Iraqi accusations, saying it is working to help stabilize its neighbor. Mehdi Dakhlallah, Syria's information minister, says it is impossible to monitor the activities of all Iraqis who have entered Syria since the war. "Syria has always been open to all Arabs, and if they have the correct documents, they can enter," he says. "But we can't read their minds about what they are going to do once they are here."

There are officially 250,000 to 300,000 Iraqis living in Syria, although the International Organization for Migration says the figure may be much higher. They include former Baathists, businessmen, Kurds, and Christians fleeing persecution.

Most of the wealthier Iraqi exiles have settled in the affluent Mezzeh district of Damascus. Driving expensive cars and dining in pricey restaurants, the new arrivals have sent property prices soaring.

Complicating matters for the Syrian authorities is the suspicion that some former officers in the Iraqi intelligence services entered Syria using fake passports.

Most Sunni Iraqi exiles openly profess their support for the resistance in Iraq.

Ahmad Dulaimi's membership in the Baath Party cost him his job teaching at Baghdad University, a victim of the de-Baathification program of the now-defunct Coalition Provisional Authority. Originally from Fallujah, he moved to Damascus last year and earns a small living writing for Al-Moharer, a pro-Baathist website which advocates armed resistance in Iraq.

"Everyone supports the resistance here, Sunnis, Shiites, and Christians," he says. "Resistance is the only weapon to free Iraq and free our prisoners."

Among those mentioned by the exiles as leaders of the reorganized Iraqi Baath party are Sabawi Ibrahim, a half-brother of Saddam Hussein who once headed the Iraqi intelligence service; Mohammed Younis al-Ahmed, secretary-general of the Iraqi Baath party regional command; and Fawzi al-Rawi, a businessman. The US is offering $1 million rewards for information leading to the arrests of the first two men.

Many Iraqi exiles say that Syria is being unfairly singled out for criticism when there are many more Iraqi Baathists, including senior figures, living in Jordan.

"We are very surprised that everyone accuses Damascus, when most of the senior Baathists are in Amman," says Mohammed Said, the representative in Damascus of the Supreme Council for the Islamic Revolution in Iraq, a Shiite party.

Mr. Said and other Iraqis interviewed say they believe that the Syrian government does not facilitate the activities of the Iraqi Baathists, instead blaming individual Syrian Baathists who share an ideological affinity with their Iraqi counterparts. Syria's regime is a separate branch of the Baath party that ruled Mr. Hussein's Iraq.

The Syrian regime is no longer the monolithic entity it was under the leadership of former President Hafez al-Assad. President Assad, who died in 2000 and was replaced by his son Bashar, kept a firm grip on the regime. But since 2000, new power centers have emerged, a mix of old regime figures, the intelligence services, and powerful business interests.

"I think the Syrian leadership does not know all the details of what's going on," says Mr. Allawi, the Iraqi ambassador. "The problem in Syria is that there are so many security branches that one doesn't know what the other is doing."

It is a problem that seems to be recognized by the Syrian government. Interior minister Ghazi Kenaan is reportedly trying to reform the intelligence services and bring them under a centralized command.